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Learning Outline

Integumentary System

Integumentary system

Integument

Integument = skin

Only one organ in this system—but it’s the largest organ of the body

Therefore, the skin is an organ AND a system

A few biologists designate nails, hairs, and/or the fatty layer under the skin as separate organs that are part of the integument—but here, we take the more common approach to designate the skin proper as the single organ of this system

Skin color

Genetic factors

Environmental factors

Tattoos involve embedding dyes into the dermis, thus changing the color of the skin’s appearance. It may be done for cosmetic reasons (e.g. body art or permanent makeup), reconstruction (e.g. areola replacement after mastectomy). identification (e.g. to identify body donors or prisoners), or (pictured here) to help one learn anatomy. Click on the image to enlarge it.

Physiological factors

Examples:

ß-carotenes from food

Hormones such as ACTH (adrenocorticotropic hormone) and other molecules related to melanocortins

Blood volume/color

Oxyhemoglobin is bright red; carbaminohemoglobin is dark red

Cyanosis is bluish color of skin from dark red blood

Jaundice (bile pigments build up in skin)

Human skin color varies widely, mostly from the presence of different types and amounts of melanin in the epidermis, as seen in these three photos of young girls.

Left are Maasai girls from Tanzania, Africa.
Middle are villagers from the upper Amazon, Peru.
Right is my daughter Aileen (Euro-american) in 1994.
Click the image to enlarge it

A strange case of the blues . . .

Stan Jones, the Libertarian candidate in Montana for the U.S. Senate in 2002, turned blue from taking home-made colloidal silver solution. He took the solution as a preventive antibacterial agent. It caused argyria, which caused silver crystals to form in his skin which, along with stimulated melanin production, made Mr. Jones’s skin look gray-blue.

Radiation

Evaporation

When water turns to steam (evaporation) heat moves (from skin) to the water molecules as they leave as water vapor

Click each photo to enlarge it

The African elephant (above) provides an extreme example of the skin’s thermoregulatory function. The front of the animal’s ear (left photo) shows the ear’s great size relative to its head and body—but very thick skin. Notice the lighter areas—these are highly keratinized patches. The back of the ear reveals very large vessels near the surface of the very thin skin (no light patches). The elephant can regulate heat loss through its ears by exposing or not exposing the back of the ear.

Remember! Human body temperature varies!

Carl Wunderlich studied body temperatures of thousands of people way back in 1868 and pronounced the average human body temperature (oral) to be 98.6 °F (37.0 °C).

However, in 1992, P.A. Mackowiak’s research team used modern equipment and techniques and found that the human body temperature (oral) averages about 98.2 °F (36.8 °C). Here are their overall results:

What does this tell us? That body temperature, and other physiological variables, are not the same for everyone and even vary within an individual. This variability is NORMAL.

NOTE: Even though Wunderlich’s average body temperature has been revised to a slightly different number by Mackowiak’s more recent work, we usually still use the older numbers for the sake of discussion—a “ball park” number—neither average applies to any particular individual.